Reed associated light sensitive apparatus for monitoring weft thread in a loom

ABSTRACT

An apparatus for the arrival monitoring of a weft in a jet loom with a reed pivotal between a first position and a second position. The reed has a longitudinal channel for the weft. An arm is mounted on the reed with the free end of the arm in the proximity of the longitudinal channel. The free end supports a light source and two light-sensitive elements. The light source is directed towards a central part of the channel for illuminating the rear portion of the channel. One light-sensitive element is directed towards the upper corner of the channel, while the other light-sensitive element is directed towards the lower corner of the channel.

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus for monitoring, preferablyarrival monitoring, of the weft, e.g. the weft thread, in a loom ofsubstantially the type in which the weft is driven through the shed withthe aid of a jet, preferably a gas jet, e.g. an air jet, and which has areed which is constructed from a number of lamellae disposed verticallywith spacing, and which is pivotal between a first position and a secondposition and has a longitudinal channel for the weft.

Prior art arrival indicators suffer from an unreliable function whichmanifests itself primarily in many error signals and in many missedactual error trigger situations. These problems are accentuatedparticularly in air powered looms, so-called jet looms, which areextraordinarily quick and operate at high speeds such as 20 picks persecond, in which event the arrival sensing must be executed duringapproximately 10-15 per cent of a complete machine cycle (5 per cent ofthe revolution). This naturally places extreme demands on the indicatoritself and the associated electronics, in particular as regardssensitivity and speed. A major inconvenience in prior art arrivalindicators is a very high degree of wear, which necessitates replacementof the indicator after short operational lives such as one month.

SUMMARY OF THE INVENTION

The task forming the basis of the present invention is to obviate thedrawbacks inherent in prior art arrival indicators to as high a degreeas possible.

The present invention realizes an arrival indicator which, with greatreliability, may be employed in the most rapid jet looms or air poweredlooms in that the weft thread is sensed not only during a single instantof time but during a given period of time. This affords: in addition, aneffective possibility to distinguish between the passage of some otherforeign matter than a weft thread and the presence of the weft threadproper, whereby the risk of confusion is precluded. The apparatusaccording to the present invention further makes possible monitoring ofwhether an excessively long weft thread has been blown through the wovenfabric and the end has become more or less jumbled at the edge of thefabric. Moreover, the apparatus according to the present inventionpermits sensing of such threads as have hitherto not been possible tosense in prior art optical indicators, e.g. non-reflective threads. Anapparatus according to the present invention will not be subjected toany major degree of wear, whereby the service life of an apparatusaccording to the present invention has been greatly extended. It is alsopossible to employ the apparatus according to the present invention forcontrolling the air emission in the loom, since the indicator or theapparatus according to the present invention sees the entire channel orhomogeneously into the entire channel and it thereby becomes possible toestablish the exact arrival time of the thread with a very high degreeof accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be described in greater detailhereinbelow, with particular reference to the accompanying Drawings.FIG. 1 schematically illustrates a vector diagram of a machine cycle.FIG. 2 is a side elevation of a reed with an apparatus according to thepresent invention in different positions during a machine cycle. FIG. 3is a side elevation of a part of an apparatus according to the presentinvention. FIG. 4 shows a section taken along the line A--A in FIG. 3.FIG. 5 shows a section taken along the line B--B in FIG. 3. FIG. 6 showsa section taken along the line C--C in FIG. 3. FIG. 7 is a sideelevation of the part illustrated in FIG. 3 seen from the opposite side.FIG. 8 is a front elevation of the part of an apparatus according to thepresent invention illustrated in FIG. 3. FIG. 9 is a schematic diagramof a part of the electronic circuitry in which an apparatus according tothe present invention is included. FIG. 10 is a side elevation of a reedwith an apparatus according to another embodiment of the presentinvention. FIG. 11 is a view from the left in FIG. 10 of a part of theapparatus according to the present invention. FIG. 12 shows a sectiontaken along the line XII--XII in FIG. 11. FIG. 13 shows a section takenalong the line XIII--XIII in FIG. 11.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of an apparatus according to the present invention will bedescribed more closely hereinbelow in connection with a jet loom or airpowered loom. Such looms are well known in the art and will not,therefore, be described in-depth here, but only those parts which aredirectly related to the apparatus according to the present inventionwill be described in detail. These parts are shown in greater detail inFIG. 2 and consist of a reed which includes a relatively large number oflamellae 1 which are disposed upstanding and with spacing on a beam 2.The upper ends of the lamellae 1 are secured in a U-shaped rail 3 andthe lower ends of the lamellae 1 are secured in a U-shaped rail 4. Thepack consisting of the lamellae 1 and the rails 3 and 4 is positionedwith the U-shaped rail 4 in a groove 5 in the beam 2 and is clamped inthe groove 5 with the aid of one or more keys or wedges 6. Warp threads(not shown) extend in the space between the lamellae 1 and together witha plurality of weft threads (not shown) form a woven fabric (not shown).

FIGS. 1 and 2 illustrate more closely a machine cycle or a machinerevolution and the movements of the parts in question during one suchmachine cycle or one such machine revolution. From the start of amachine cycle at "A" or 0°, the reed moves as illustrated in FIG. 2slowly to position I or "B". The degree division of a machine cycledescribed herein is merely by way of exemplification and other degreedivisions can be applied in different types of machines. On insertingthe weft thread with the aid of an air jet, it will be located in thechannel 7 formed in the lamellae 1 at least at the end of its path ofmovement or at the fabric edge where it is desirable to establish thepresence or arrival of the weft thread, for which reason an apparatusaccording to the present invention is placed at this point, as isapparent in FIG. 2.

That point in time at which the weft thread occurs in the channel 7behind the free end of an arm 8 is not predeterminable to 100 per centbut should occur between the positions "B" and "C" in FIGS. 1 and 2.These positions may vary from loom to loom and are dependent uponmanufacture and settings, for which reason no determined degree figuretherefore is given here. During the period of time from position "B" to"C", the reed is in motion from position I to II (FIG. 2). Afterposition "C", it is considered to be too late for a normal arrival ofthe weft thread, since the reed in this position has approached tooclose to the fabric edge. The apparatus according to the presentinvention is to monitor or check that the weft thread is located in thechannel 7 and thereby between the free end of the arm 8 and the rearedge or bottom of the channel 7 in the period of time between positions"B" and "C".

The machine cycle naturally controls the apparatus according to thepresent invention and is synchronized with some type of sensor, forexample an inductive or optical sensor which is coupled to the loom insuch a manner that a "flag signal" (logic signal) is established atposition "A" and cancelled at position "C". This arrangement is wellknown in the art and will not be described in greater detail here.

The arm 8 in the illustrated embodiment of an apparatus according to thepresent invention is mounted on the beam 2 with the aid of mountingfittings 9 and an Allen bolt 10. The mounting fittings 9 and the bolt 10permit orientation positioning of the arm 8 so that the free end of thearm 8 will be placed in a suitable manner ahead of the longitudinalchannel 7 in the reed, as illustrated in FIG. 2. FIG. 2 also intimateswith solid lines three optical axes 11, 12 and 13 as well as that anglewhich each respective optical axis makes with the longitudinal axis ofthe arm 8 seen from the side or the projection illustrated in FIG. 2.These angles are, moreover, shown in greater detail in FIG. 3.

The arm 8 is shown in greater detail in FIGS. 3-8, FIGS. 4, 5 and 6showing respectively sections A--A, B--B and C--C in FIG. 1 on a largerscale. The above-mentioned optical axes 11, 12 and 13 are shown in thesections. In FIG. 3, it is more clearly apparent that the optical axis11 makes an angle of 50°-60°, preferably 56°, with the longitudinal axisof the arm 8, while the optical axis 12 makes an angle with thelongitudinal axis of the arm 8 of 60°-70°, preferably 65°, and theoptical axis 13 makes an angle with the longitudinal axis of the arm 8of 40°-50°, preferably 44°. The arm 8 displays, at its free end, aplanar surface 14 which makes an angle of 40°-45°, preferably 42°, withthe longitudinal axis of the arm 8. The free end of the arm 8 isterminated by a further planar surface 15 which makes an angle of60°-70° , preferably 65°, with the longitudinal axis of the arm 8. Theabove-mentioned angles can, naturally, vary from design to design,depending upon the appearance and dimensions of the longitudinal channel7 in the reed, which may vary from machine design to machine design.

In the free end of the arm 8, there is provided a recess 16 whichdischarges in the surface 14 and is intended for a light source in theform of a suitable LED. The recess 16 is oriented such that the opticalaxis, of the LED placed therein coincides with the optical axis 11 whichis shown by ghosted lines. In the free end of the arm 8, there isfurther provided a recess 17 which discharges in the planar surface 14and is intended for a light-sensitive element in the form of a suitablephototransistor TR1. The recess 17 is oriented such that the opticalaxis of the phototransistor TR1 placed therein coincides with theoptical axis 12 which is shown by ghosted lines. In the free end of thearm 8, there is further provided a recess 18 which discharges in theplanar surface 14 and is intended for yet a further light-sensitiveelement in the form of a phototransistor TR2 and which is aligned suchthat the optical axis of the phototransistor TR2 coincides with theintimated optical axis 13 which is shown by ghosted lines. As referenceline, the longitudinal axis of the arm 8 is shown in the various DrawingFIGS. 4, 5, 6 and 8 in the form of a ghosted line 19. In FIGS. 4, 5 and6, it is shown that the optical axes 11, 12 and 13 intersect one anotherat a point 20 which is also designated the focal point for the lightsource and the light-sensitive elements.

Through the focal point 20, there extends a normal 21 to the planarsurface 14 and, in FIG. 4, it is shown that the optical axis 13 makes anangle with the normal 21 of 12°-16°, preferably 14°. In FIG. 5 it isshown that the optical axis 11 makes an angle of 5°-10°, preferably 7°,with the normal 21, and in FIG. 6 it is apparent that the optical axis12 makes an angle of 20°-25°, preferably 22°, with the normal 21. Thearm 8 is oriented such that the focal point 20 is located approx. 1 mmahead of the distal edge in the channel 7.

FIG. 7 shows the arm 8 from the opposite side relative to FIG. 3, whileFIG. 8 shows the arm 8 from the front. In the arm 8, there are furtheraccommodated holes 22 and 23, recesses 24 and 25 and a milling 26 formounting and placing of, for example, electronic components.

As is particularly apparent from FIG. 2, the light source will, with itsoptical axis 11, illuminate the rear edge or bottom in the longitudinalchannel 7 in the reed. The light source or LED must be of the wideradiating type for relatively uniform illumination of the bottom or therear edge in the channel 7. It is further apparent from FIG. 2 that theoptical axis 12 of the light-sensitive element or phototransistor TR1 isdirected towards the lower corner in the longitudinal channel 7 or thelower edge of the bottom in the longitudinal channel 7. The optical axis13 of the light-sensitive element or phototransistor TR2 is directedtowards the upper corner in the longitudinal channel 7 or the upper edgeof the bottom in the longitudinal channel 7. The light-sensitiveelements or phototransistors TR1 and TR2 should advantageously havenarrow sensitivity lobes. The optical axis 11 of the light source or LEDimpinges as well centrally on the bottom of the longitudinal channel 7or centrally on the rear edge in the longitudinal channel 7 between theupper corner and the lower corner. Hereby, the entire bottom or rearedge in the longitudinal channel 7 will be illuminated and there will beobtained a reflection from the entire rear edge or bottom in thelongitudinal channel 7.

The electronic elements in the form of the LED and the phototransistorsTR1 and TR2 are coupled into a suitable electronic circuit for drivingthe light source with a carrier wave signal of a frequency of a few kHz,while the phototransistors are coupled into a circuit of, for example,the type illustrated in FIG. 9 which is a per se known signal chargingcircuit. The phototransistor TR1 is coupled to the negative input of anoperational amplifier OP via a potentiometer P1 and a capacitor C1, andthe phototransistor TR2 is coupled to the negative input of theoperational amplifier OP via a potentiometer P2 and a capacitor C2. Thepotentiometers P1 and P2 serve for suitable adjustment of the amplitudeof the signal obtained on the output from the operational amplifier OP.The amplitude of the signal will reflect changes in the light reflectionon the two phototransistors TR1 and TR2 because of the presence of athread or a weft in the channel 7, whereafter the amplitude change inthe signal can be evaluated with the aid of a suitable electroniccircuit which is included in a central unit for the loom. If the signalfrom the operational amplifier OP does not satisfy the criteria set bythe electronic circuitry, an error function will be triggered, and thiscan entail knock-off or arrest of the loom.

In that case where it is desirable to operate at higher frequencies thana few kHz, it may be appropriate to replace the phototransistors byphotodiodes which are more rapid than the phototransistors. In certaincases, it may be appropriate to replace the two potentiometers by asingle potentiometer which is coupled in between the phototransistorsand whose slider is connected to earth.

The embodiment of the present invention illustrated in FIGS. 10-13corresponds in principle to the above-described embodiment and differssubstantially from the above-described embodiment in that the recesses17' and 18' for the phototransistors TR1 and TR2 are locatedsubstantially straight above one another, and in that the optical axes11', 12' and 13' make other angles with the longitudinal axis 19' of thearm 8' than in the above-described embodiment.

In this new embodiment, the optical axis 11' for the recess 16' makes anangle of 45°-55°, preferably 48°, with the longitudinal axis 19 of thearm 8', which is located in the surface of the arm 8' facing towards thereed, as is apparent in FIG. 12. The recess 16' is intended for an LED,as in the above-described embodiment. Seen in the projection shown inFIG. 11, the optical axes 11', 12' and 13' make an angle of 10°-15°,preferably 13°, with the longitudinal axis 19 of the arm 8'. The pointof intersection between the axes 11', 12' and 13' forms the focal point20'.

FIG. 10 shows, in addition to the parts illustrated in FIG. 2, also atemple 27 which does not constitute any part of the invention properaccording to this disclosure.

The major advantage of the present invention is that thephototransistors TR1 and TR2 are located in substantially the sameplane, whereby scanning of the channel 7 will be considerably moreexact. Furthermore, the arm 8' can be given a somewhat more slender andabove all more compact design and construction.

I claim:
 1. An apparatus for monitoring of the weft in a loom of thetype in which the weft is driven through the shed of the loom with theaid of a jet and which has a reed pivotally disposed for pivotingbetween a first position and a second position, the reed having alongitudinal channel for the weft, said apparatus comprising an armhaving a free end adapted to be located in the proximity of thelongitudinal channel in the reed; and means at the arm free end forholding a light source and two light-sensitive elements, with the lightsource directed towards the channel for illuminating a rear portion ofthe channel, and with one light-sensitive element directed towards anupper corner of the channel, and the other light-sensitive elementdirected towards a lower corner of the channel.
 2. The apparatus asclaimed in claim 1, further comprising a light source and twolight-sensitive elements held by said holding means, wherein the lightsource is wide radiating for illuminating substantially an entire rearedge or the bottom in the longitudinal channel in the reed, so that theentire rear of the channel or bottom is included as a reflector, andwherein the light-sensitive elements have narrow sensitivity lobes. 3.The apparatus as claimed in claim 1, wherein the arm is adapted to bemounted on a lower portion of the reed so as to extend up towards thelongitudinal channel in the reed.
 4. The apparatus as claimed in claim1, wherein said holding means comprises a first recess in the free endof the arm for holding the light source, and second and third recessesin the free end of the arm for holding the light-sensitive elements. 5.The apparatus as claimed in claim 4, further comprising a light sourceand two light-sensitive elements held by said holding means, wherein thelight source is an LED of the wide radiating type and thelight-sensitive elements are phototransistors with narrow sensitivitylobes.
 6. The apparatus as claimed in claim 5, further comprising asignal charging circuit including an operational amplifier for havingthe light-sensitive elements incorporated therein to generate anamplitude-varying signal via the operational amplifier.
 7. The apparatusas claimed in claim 4, wherein the recesses are adapted to hold thelight source and the light-sensitive elements with optical axes of thelight source and the light-sensitive elements oriented in discretedirections.
 8. The apparatus as claimed in claim 7, wherein the firstrecess is adapted to hold the light source with an optical axis of thelight source making an angle of substantially 13° with the longitudinalaxis of the arm as seen from the front of the arm, and the second andthird recesses area adapted to hold the two light-sensitive elementswith optical axes of the two light-sensitive elements making an angle ofsubstantially 13° with the longitudinal axis of the arm as seen from thefront of the arm.
 9. The apparatus as claimed in claim 8 wherein the armis adapted to be mounted in a lower portion of the reed so as to extendup towards the longitudinal channel in the reed such that focal pointsof the light source and the two light-sensitive elements lie a distancefrom the rear edge or bottom in the longitudinal channel in the reed.10. The apparatus as claimed in one of claims 4 and 7, wherein the firstrecess is adapted to hold the light source with an optical axis of thelight source making an angle of substantially 48° with the longitudinalaxis of the arm as seen from one side of the arm, the second recess isadapted to hold one light-sensitive element with an optical axis of saidone light-sensitive element making an angle of substantially 56° withthe longitudinal axis of the arm as seen from said one side, and thethird recess is adapted to hold the other light-sensitive element withan optical axis of said other light-sensitive element making an angle ofsubstantially 20° with the longitudinal axis of the arm as seen fromsaid one side.
 11. The apparatus as claimed in claim 10, wherein thefirst recess is adapted to hold the light source with an optical axis ofthe light source making an angle of substantially 13° with thelongitudinal axis of the arm as seen from the front of the arm, and thesecond and third recesses are adapted to hold the two light-sensitiveelements with optical axes of the two light-sensitive elements making anangle of substantially 13° with the longitudinal axis of the arm as seenfrom the front of the arm.
 12. The apparatus as claimed in claim 11wherein the arm is adapted to be mounted in a lower portion of the reedso as to extend up towards the longitudinal channel in the reed suchthat focal points of the light source and the two light-sensitiveelements lie a distance from the rear edge or bottom in the longitudinalchannel in the reed.
 13. The apparatus as claimed in claim 4, whereinthe first recess is adapted to hold the light source with an opticalaxis of the light source making an angle of substantially 13° with thelongitudinal axis of the arm as seen from the front of the arm, and thesecond and third recesses are adapted to hold the two light-sensitiveelements with the optical axes of the two light-sensitive elementsmaking an angle of substantially 13° with the longitudinal axis of thearm as seen from the front of the arm.
 14. The apparatus as claimed inclaim 13 wherein the arm is adapted to be mounted in a lower portion ofthe reed so as to extend up towards the longitudinal channel in the reedsuch that focal points of the light source and the two light-sensitiveelements lie a distance from the rear edge or bottom in the longitudinalchannel in the reed.
 15. The apparatus as claimed in claim 1, furthercomprising a signal charging circuit including an operational amplifierfor having the light-sensitive elements incorporated therein to generatean amplitude-varying signal via the operational amplifier.
 16. Theapparatus as claimed in claim 15, further comprising a light source andtwo light-sensitive elements held by said holding means, wherein thelight source is an LED of the wide radiating type and thelight-sensitive elements are phototransistors with narrow sensitivitylobes.
 17. The apparatus as claimed in claim 1, further comprising alight source and two light-sensitive elements held by said holdingmeans, wherein the light source is an LED of the wide radiating type andthe light-sensitive elements are phototransistors with narrowsensitivity lobes.